/*
 *  DTLS cookie callbacks implementation
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 *
 *  This file is provided under the Apache License 2.0, or the
 *  GNU General Public License v2.0 or later.
 *
 *  **********
 *  Apache License 2.0:
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  **********
 *
 *  **********
 *  GNU General Public License v2.0 or later:
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  **********
 */
/*
 * These session callbacks use a simple chained list
 * to store and retrieve the session information.
 */

#if !defined(MBEDTLS_CONFIG_FILE)
#include "nettls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#if defined(MBEDTLS_SSL_COOKIE_C)

#if defined(MBEDTLS_PLATFORM_C)
#include "nettls/platform.h"
#else
#define mbedtls_calloc calloc
#define mbedtls_free   free
#endif

#include "nettls/ssl_cookie.h"
#include "nettls/ssl_internal.h"
#include "nettls/platform_util.h"

#include <string.h>

/*
 * If DTLS is in use, then at least one of SHA-1, SHA-256, SHA-512 is
 * available. Try SHA-256 first, 512 wastes resources since we need to stay
 * with max 32 bytes of cookie for DTLS 1.0
 */
#if defined(MBEDTLS_SHA256_C)
#define COOKIE_MD        MBEDTLS_MD_SHA224
#define COOKIE_MD_OUTLEN 32
#define COOKIE_HMAC_LEN  28
#elif defined(MBEDTLS_SHA512_C)
#define COOKIE_MD        MBEDTLS_MD_SHA384
#define COOKIE_MD_OUTLEN 48
#define COOKIE_HMAC_LEN  28
#elif defined(MBEDTLS_SHA1_C)
#define COOKIE_MD        MBEDTLS_MD_SHA1
#define COOKIE_MD_OUTLEN 20
#define COOKIE_HMAC_LEN  20
#else
#error "DTLS hello verify needs SHA-1 or SHA-2"
#endif

/*
 * Cookies are formed of a 4-bytes timestamp (or serial number) and
 * an HMAC of timestemp and client ID.
 */
#define COOKIE_LEN (4 + COOKIE_HMAC_LEN)

void mbedtls_ssl_cookie_init(mbedtls_ssl_cookie_ctx* ctx)
{
    mbedtls_md_init(&ctx->hmac_ctx);
#if !defined(MBEDTLS_HAVE_TIME)
    ctx->serial = 0;
#endif
    ctx->timeout = MBEDTLS_SSL_COOKIE_TIMEOUT;

#if defined(MBEDTLS_THREADING_C)
    mbedtls_mutex_init(&ctx->mutex);
#endif
}

void mbedtls_ssl_cookie_set_timeout(mbedtls_ssl_cookie_ctx* ctx, unsigned long delay)
{
    ctx->timeout = delay;
}

void mbedtls_ssl_cookie_free(mbedtls_ssl_cookie_ctx* ctx)
{
    mbedtls_md_free(&ctx->hmac_ctx);

#if defined(MBEDTLS_THREADING_C)
    mbedtls_mutex_free(&ctx->mutex);
#endif

    mbedtls_platform_zeroize(ctx, sizeof(mbedtls_ssl_cookie_ctx));
}

int mbedtls_ssl_cookie_setup(mbedtls_ssl_cookie_ctx* ctx, int (*f_rng)(void*, unsigned char*, size_t), void* p_rng)
{
    int ret;
    unsigned char key[COOKIE_MD_OUTLEN];

    if ((ret = f_rng(p_rng, key, sizeof(key))) != 0)
        return (ret);

    ret = mbedtls_md_setup(&ctx->hmac_ctx, mbedtls_md_info_from_type(COOKIE_MD), 1);
    if (ret != 0)
        return (ret);

    ret = mbedtls_md_hmac_starts(&ctx->hmac_ctx, key, sizeof(key));
    if (ret != 0)
        return (ret);

    mbedtls_platform_zeroize(key, sizeof(key));

    return (0);
}

/*
 * Generate the HMAC part of a cookie
 */
static int ssl_cookie_hmac(
    mbedtls_md_context_t* hmac_ctx,
    const unsigned char time[4],
    unsigned char** p,
    unsigned char* end,
    const unsigned char* cli_id,
    size_t cli_id_len)
{
    unsigned char hmac_out[COOKIE_MD_OUTLEN];

    MBEDTLS_SSL_CHK_BUF_PTR(*p, end, COOKIE_HMAC_LEN);

    if (mbedtls_md_hmac_reset(hmac_ctx) != 0 || mbedtls_md_hmac_update(hmac_ctx, time, 4) != 0
        || mbedtls_md_hmac_update(hmac_ctx, cli_id, cli_id_len) != 0 || mbedtls_md_hmac_finish(hmac_ctx, hmac_out) != 0) {
        return (MBEDTLS_ERR_SSL_INTERNAL_ERROR);
    }

    memcpy(*p, hmac_out, COOKIE_HMAC_LEN);
    *p += COOKIE_HMAC_LEN;

    return (0);
}

/*
 * Generate cookie for DTLS ClientHello verification
 */
int mbedtls_ssl_cookie_write(void* p_ctx, unsigned char** p, unsigned char* end, const unsigned char* cli_id, size_t cli_id_len)
{
    int ret;
    mbedtls_ssl_cookie_ctx* ctx = (mbedtls_ssl_cookie_ctx*)p_ctx;
    unsigned long t;

    if (ctx == NULL || cli_id == NULL)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    MBEDTLS_SSL_CHK_BUF_PTR(*p, end, COOKIE_LEN);

#if defined(MBEDTLS_HAVE_TIME)
    t = (unsigned long)mbedtls_time(NULL);
#else
    t = ctx->serial++;
#endif

    (*p)[0] = (unsigned char)(t >> 24);
    (*p)[1] = (unsigned char)(t >> 16);
    (*p)[2] = (unsigned char)(t >> 8);
    (*p)[3] = (unsigned char)(t);
    *p += 4;

#if defined(MBEDTLS_THREADING_C)
    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
        return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret);
#endif

    ret = ssl_cookie_hmac(&ctx->hmac_ctx, *p - 4, p, end, cli_id, cli_id_len);

#if defined(MBEDTLS_THREADING_C)
    if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
        return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + MBEDTLS_ERR_THREADING_MUTEX_ERROR);
#endif

    return (ret);
}

/*
 * Check a cookie
 */
int mbedtls_ssl_cookie_check(void* p_ctx, const unsigned char* cookie, size_t cookie_len, const unsigned char* cli_id, size_t cli_id_len)
{
    unsigned char ref_hmac[COOKIE_HMAC_LEN];
    int ret = 0;
    unsigned char* p = ref_hmac;
    mbedtls_ssl_cookie_ctx* ctx = (mbedtls_ssl_cookie_ctx*)p_ctx;
    unsigned long cur_time, cookie_time;

    if (ctx == NULL || cli_id == NULL)
        return (MBEDTLS_ERR_SSL_BAD_INPUT_DATA);

    if (cookie_len != COOKIE_LEN)
        return (-1);

#if defined(MBEDTLS_THREADING_C)
    if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0)
        return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + ret);
#endif

    if (ssl_cookie_hmac(&ctx->hmac_ctx, cookie, &p, p + sizeof(ref_hmac), cli_id, cli_id_len) != 0)
        ret = -1;

#if defined(MBEDTLS_THREADING_C)
    if (mbedtls_mutex_unlock(&ctx->mutex) != 0)
        return (MBEDTLS_ERR_SSL_INTERNAL_ERROR + MBEDTLS_ERR_THREADING_MUTEX_ERROR);
#endif

    if (ret != 0)
        return (ret);

    if (mbedtls_ssl_safer_memcmp(cookie + 4, ref_hmac, sizeof(ref_hmac)) != 0)
        return (-1);

#if defined(MBEDTLS_HAVE_TIME)
    cur_time = (unsigned long)mbedtls_time(NULL);
#else
    cur_time = ctx->serial;
#endif

    cookie_time = ((unsigned long)cookie[0] << 24) | ((unsigned long)cookie[1] << 16) | ((unsigned long)cookie[2] << 8) | ((unsigned long)cookie[3]);

    if (ctx->timeout != 0 && cur_time - cookie_time > ctx->timeout)
        return (-1);

    return (0);
}
#endif /* MBEDTLS_SSL_COOKIE_C */
